A stepped-FM coded radar for vehicular collision avoidance is proposed providing anti-interference capability and high range-resolution. Wide-band voltage controlled oscillator (VCO) devices have in general a linearit...
详细信息
A stepped-FM coded radar for vehicular collision avoidance is proposed providing anti-interference capability and high range-resolution. Wide-band voltage controlled oscillator (VCO) devices have in general a linearity error over the bandwidth, which is a critical issue for high range-resolution radar. We also suggest a compensation scheme based on an least mean square (LMS) method for the VCO linearity error.
In this work we report the simulated performance of two digital wireless systems, designed for the transmission on a time selective Rayleigh flat fading channel. In the first system a four-dimensional trellis coded mo...
详细信息
In this work we report the simulated performance of two digital wireless systems, designed for the transmission on a time selective Rayleigh flat fading channel. In the first system a four-dimensional trellis coded modulation with a non-coherent detection method, formed by a differential demodulator followed by a MLSE-type Viterbi decoder, has been adopted. The second system consists of a continuous phase modulation of GMSK type demodulated through a non-coherent detection method formed by a frequency discriminator followed by an estimator based on the Chung algorithm.
A new design algorithm for integrated digital transmission systems operating over noisy channels has been developed. Taking all system design aspects into consideration, the algorithm provides a general methodology fo...
详细信息
A new design algorithm for integrated digital transmission systems operating over noisy channels has been developed. Taking all system design aspects into consideration, the algorithm provides a general methodology for designing a typical digital communication system as a whole. Based on information-theoretic principles and on practical system design restrictions, the algorithm first eliminates design options that are unacceptable. A set of system configurations, i.e., the key parameters for the source/channel coding and modulation subsystems, are then generated for acceptable overall system designs. A large variety of existing methods for source coding, error-correction coding and modulation can be used in conjunction with the proposed system design algorithm. Applications to speech and image transmission have been considered as concrete examples for communication systems designed in accordance with this algorithm. Simulations have demonstrated that the system design algorithm can efficiently reduce the number of design options to a limited set of acceptable options with corresponding key parameters specifically identified. The methodology described in this paper provides communication engineers with means to rapidly produce the best possible system design configurations.
We estimate the weight enumerator of a product code by using an exact expression for its known terms (e.g., the number of low weight words), and a binomial approximation for its unknown terms. We subsequently apply a ...
详细信息
We estimate the weight enumerator of a product code by using an exact expression for its known terms (e.g., the number of low weight words), and a binomial approximation for its unknown terms. We subsequently apply a union bound, using the estimated weight enumerator, to large product codes. The computed union bounds are similar to the simulation results of iterative (turbo) decoding of such codes as reported in literature.
We describe an iterative detection and decoding scheme for the uplink in a convolutionally coded direct sequence code division multiple access (DS-CDMA) system. We consider maximum-a-posteriori (MAP) decoding and redu...
详细信息
We describe an iterative detection and decoding scheme for the uplink in a convolutionally coded direct sequence code division multiple access (DS-CDMA) system. We consider maximum-a-posteriori (MAP) decoding and reduce the complexity through an iterative interference cancelation scheme combined with a suboptimal channel decoding algorithm. The MAP priors are updated at every iteration step. We investigate the performance of this low complexity scheme and observe that it is close to optimal.
The development of adaptive trellis coded modulation schemes for communication systems operating over time-varying Rayleigh fading channels is considered. If the system employs a single outdated noiseless channel esti...
详细信息
The development of adaptive trellis coded modulation schemes for communication systems operating over time-varying Rayleigh fading channels is considered. If the system employs a single outdated noiseless channel estimate and is able to achieve perfect interleaving of the coded symbols, substantial throughput gains are observed over non-adaptive trellis coded modulation schemes for systems with low user mobility. Next, the effect of noise in the channel estimates is shown to be an important consideration, even at the relatively high signal-to-noise ratios considered here. Finally, a bound to the pairwise error probability between two paths in the trellis of the adaptive scheme is derived analytically for the case where the coded symbols are imperfectly interleaved; this result suggests that adaptive signaling may be a strong candidate for systems operating in an environment that has limited diversity available.
Advances in modern DSP techniques provide a means for intercepting smart covert signal emitters by taking account of the structural properties of their waveform and/or spectra. Previous research has shown that higher-...
详细信息
Advances in modern DSP techniques provide a means for intercepting smart covert signal emitters by taking account of the structural properties of their waveform and/or spectra. Previous research has shown that higher-order statistical processing can detect and characterise direct-sequence spread-spectrum signals. Triple correlation analysis is able to detect m-sequence chip codes and also estimate the associated generator polynomials. The process works with full code frames and partial coded windows in noisy data modulated channels. The research reported concentrates on an investigation into various statistical methods for discriminating multiple DS/SS code sequences and also search techniques for blind detection of m-sequences where none of the code parameters is known to the intercept receiver in advance.
In this work we consider the problem of combined source-channel coding for H.263 coded video transmitted over a wireless channel which is modeled as a slow-fading Rician channel. As wireless channels are generally ban...
详细信息
In this work we consider the problem of combined source-channel coding for H.263 coded video transmitted over a wireless channel which is modeled as a slow-fading Rician channel. As wireless channels are generally bandwidth limited, the specific channel coding scheme employed here is non-binary bandwidth-efficient trellis-coded modulation (TCM) employing appropriate phase-shift keyed modulation. We describe a methodology for determining the optimal tradeoff between source and channel coding as a function of channel characteristics. In particular, if feedback on channel parameters is available, the video information can be optimally coded. In the case where feedback is not available, we illustrate the effects of using mismatched codes designed for other than the existing channel conditions.
Multilevel memory cells and analog memory cells have the capability of storing considerably more than one bit per cell. A multilevel or an analog memory cell is modelled as an additive white Gaussian noise channel. Th...
详细信息
Multilevel memory cells and analog memory cells have the capability of storing considerably more than one bit per cell. A multilevel or an analog memory cell is modelled as an additive white Gaussian noise channel. Thus storing a certain number of bits in one cell corresponds to storing a finite number of amplitude levels. Due to the additive noise in the memory cell, the bits read from the memory cell are affected by an output error probability. This paper proposes using a coded modulation technique to increase the storage capacity of multilevel and analog memory cells by one extra bit per cell. The technique can also be applied to improve the read-out bit-error probability and provide unequal error protection for the bits to be stored. One and two-dimensional coded modulation schemes as well as uncoded modulation schemes are presented in detail. Complexity issues are also considered.
We look into a new strategy for detecting signals with trellis-coded modulation transmitted over a frequency-non-selective fading channel. For both interleaved and non-interleaved systems, the Viterbi algorithm is use...
详细信息
We look into a new strategy for detecting signals with trellis-coded modulation transmitted over a frequency-non-selective fading channel. For both interleaved and non-interleaved systems, the Viterbi algorithm is used to minimize an additive metric which incorporates estimates of the fading samples in each symbol interval. Kalman estimators are used to recursively update these estimates on a per-survivor basis whereupon, at a given instant, a distinct estimate is associated to each trellis node. Bit error rate curves are evaluated by computer simulations and compared to curves obtained assuming ideal fading knowledge and to curves pertaining to other methods in the literature.
暂无评论